A manual lotion pump is generally mounted on the mouth of a container with a lotion product contained therein. By pressing the pump, a user can get some liquid, such as a lotion, pumped out of the container by the pump for a certain application. At present, there are many types of water-ingress-preventing mechanism for a lotion pump, which are used to prevent foreign liquids, such as water, from entering the container and contaminating the product in the container during the pump being operated. Those conventional water-ingress-preventing mechanisms, however, all have more or less problems that they are hardly capable of completely preventing foreign liquids from entering the lotion container.
For example, a water-ingress-preventing mechanism of a lotion pump is disclosed in China Patent CN2314128Y, as shown in FIGS. 6 and 7. That conventional water-ingress-preventing mechanism of a lotion pump is basically composed of a press head 110, a cylinder cover 120 and a connecting conduit 130. In the head 110, there is a passage 111, the lower opening of which is defined by a tube-like joint portion 112 which extends downwards vertically from the body of the press head 110. A locking tube portion 113 is formed around the joint portion 112. The upper portion of the outside wall of the locking tube portion 113 is formed with an external thread. The upper end 131 of the connecting conduit 130 is press-fitted into the joint portion 112 of the press head 110 so as to be secured to the head 110 and thereby to create a fluid communication between the connecting conduit 130 and the passage 111. In the cylinder cover 120, there is a central through-hole 121 for the connecting conduit 130 to pass. On the inside wall surface of the lower portion of the central through-hole 121 is provided with a guide sleeve 122 for preventing water ingress, which extends upwards vertically beyond the top surface of the cylinder cover 120. The inside surface of the water-ingress-preventing guide sleeve 122 is in a slide fit with the outside wall surface of the connecting conduit 130. Between the outside wall surface of the water-ingress-preventing guide sleeve 122 and the inside wall surface of the upper portion of the central through-hole 121 is formed an annular recess 124, in which the locking tube portion 113 is to be threaded. The inside wall surface of the central through-hole 121 facing to the outside wall surface of the guide sleeve 122 is formed with an internal thread, which can mate with the external thread on the locking tube portion 113 when the press head 110 is pressed so that the lower end of the locking tube portion 113 enters into the annular recess 124 and is turned, thereby locking the press head 110 relative to the cylinder cover 120.
In operation of a lotion pump with the above-mentioned water-ingress-preventing mechanism, the press head 110 is pressed from the upper stop position (USP) of a press stroke and downwards with respect to the cylinder cover 120 until the lower end edge of the locking tube portion 113 enters into the annular recess 124 between the inside wall surface of the central through-hole 121 of the cylinder cover 120 and the outside wall surface of the guide sleeve 122, and the lowermost turn of the external thread of the locking tube portion 113 is in contact with the uppermost turn of the internal thread of the central through-hole 121. The position in which the turns of threads are contacted with each other is the lower stop position (LSP) of the press stroke of the press head 110 relative to the cylinder cover 120. During a process that the press head 110 is pressed from the USP to the LSP, some liquid is pumped out of the container (not shown), and meanwhile, some atmosphere air is sucked into the container through the small clearance between the inside wall surface of the water preventing guide sleeve 122 and the outside wall surface of the connecting conduit 130 to compensate for the negative pressure due to the reduction of the liquid volume in the container. However, when the press head 110 is pressed to such an extent that the lower end of its locking tube portion 113 enters into the annular recess 124 of the cylinder cover 120, if there is some dirty water or other liquids deposited in the recess (it is generally an inevitable case in a moist place such as bathroom), the lower end of the locking tube portion 113 will dip into the deposited liquid so as to block the communication between the container inside and the atmosphere air. Thus, if the press head 110 is further pressed down, the deposited liquid will be sucked into the container and contaminate the product therein.